A known printer or copier includes a sheet supply device configured to supply a recording sheet to an image forming unit. The sheet supply device is configured to sequentially supply recording sheets while keeping a predetermined interval or distance between a trailing end of a previous recording sheet and a leading end of a next recording sheet.
In the sheet supply device, the predetermined distance may not be maintained due to a dimensional error of a diameter of a supply roller configured to feed a recording sheet or slip between a recording sheet and rollers.
For example, there is a sheet supply device including a recording sheet detection sensor configured to detect an interval or distance between a trailing end of a previous recording sheet and a leading end of a next recording sheet and a determination device configured to determine whether the detected interval or distance is longer than a predetermined interval or distance. When the determination device determines that the detected interval is longer than the predetermined interval, a supply speed of a next following recording sheet to be fed by the supply roller, e.g., rotation speed of the supply roller, is increased to reduce the interval between a trailing end of a previous recording sheet and a leading end of a next recording sheet. Nevertheless, to reduce the interval between a trailing end of a previous recording sheet and a leading end of a next recording sheet in the sheet supply device, a driving mechanism for the supply roller and a driving mechanism for a feeding roller disposed downstream of the supply roller in a sheet feeding direction need to be separately structured and separately controlled. Accordingly, motors need to be separately provided to drive the supply roller and the feeding roller, and several types of gear mechanisms to change the sheet supply speed by the supply roller and clutches to switch the gear mechanisms are required. This makes the driving mechanisms of the sheet supply device complicated.